<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>CSS边框的修饰</title>
    <style>
        div{
            /*border-top-width: 1px;*/
            /*border-top-style: dotted;*/
            /*border-top-color: red;*/
            border-top: 1px solid red;
            height: 300px;width: 300px;
        }
    </style>
</head>
<body>
    <div id="div1"></div>
</body>
</html>